Mold for molding of substrate for information recording medium

ABSTRACT

A mold for molding a plurality of substrates for an information recording medium includes a fixing member, a plurality of units fixed to the fixing member, and a molding cavity. Each of the units has a preformat pattern with a surface corresponding to information recording medium formed on its surface, and the molding cavity is disposed opposite to the units so that the preformat patterns face the molding cavity.

This application is a division of application Ser. No. 07/622,151 filedDec. 3, 1990, now U.S. Pat. No. 5,174,937.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a mold for molding when preparing a substratefor information recording medium according to the cast molding methodand to a method for preparation thereof.

2. Related Background Art

In the prior art, a substrate for information recording medium has anuneven pattern such as grooves for tracking, pits for information, etc.on the information recording surface thereof. As the method for formingthis uneven pattern on the substrate, there have been known (1) themethod in which a track groove of the stamper type is transferred by theinjection method or the hot press method when the substrate comprises athermoplastic resin, or (2) the method according to the so-called 2Pmethod, in which a photocurable resin composition is applied on atransparent resin plate comprising a thermosetting resin or athermoplastic resin, then an energy source such as UV-rays are impartedfrom the side of the transparent resin plate with the stamper moldadhered thereon to cure the above photocurable resin composition, andthe replica of the stamper mold is transferred onto the transparentresin plate.

However, the thermoplastic resin substrate obtained according to theinjection method or the hot press method of the first method has theproblem that warping or optical anisotropy of the substrate aftermolding may be caused due to residual stress or orientation of moleculesdue to thermal history during molding.

On the other hand, the substrate obtained according to the 2P method ofthe second method will frequently generate the problem of deteriorationof recording characteristics, because the polymerization initiator ormonomer to be used in photocuring is liable to remain within the resinafter photocuring, whereby they have influences on the optical recordinglayer of the recording medium.

As the method for preparing a substrate for information recording mediumis free from such problems, there has been known (3) the method in whichduring cast molding of a prepolymer containing a monomer of the resin ora solvent, cast molding is effected by use of a mold for casting havingtrack grooves formed previously on one side or both sides thereof. Thesubstrate obtained according to this method has substantially nopressure applied during molding as compared with the methods of (1) and(2). Also, thermoplastic resins, thermosetting resins and photocurableresins can be utilized as the resin for molding, and therefore a resinhaving no deleterious influence on the recording layer can be chosen.

In the third cast molding method (3), as the mold having an unevenpattern corresponding to the uneven preformat such as grooves fortracking, pits for information, etc., there has been known glass platessubjected to patterning of such unevennesses by photolithographic steps,or to patterning by laser cut, or glass plates, metal plates havingunevenness formed thereon by direct cuts with a diamond needle having asharp end, etc.

However, as a problem in cast molding, there may be low productivitybecause of very long treatment time at one time during production of thesubstrate. Accordingly, for the purpose of improving productivity, as amold to be used in the above cast molding, a mold for giving a pluralnumber of units has been demanded. However, as described above, sinceminute working is required to form unevenness on the mold for casting,in the case of manufacturing a mold for producing a plural number ofunits, the production cost will become disadvantageously high. Also,when failures such as defects, etc. occur in one pattern of a pluralnumber of pattern surfaces, there is the problem that the mold itself isno longer usable.

SUMMARY OF THE INVENTION

The present invention has been accomplished for improving such drawbacksof the cast molding of the prior art, and its object is to provide amethod for preparing substrates for information recording medium withgood productivity, and having an uneven preformat formed on the surface,which is optically isotropic without warping.

Another object of the present invention is to provide a method forpreparing substrates for an information recording medium, which canobtain substrates for information recording medium with goodproductivity, and having an uneven preformat formed on the surface andis optically isotropic without warping. And even if defects may begenerated in one unit, only that unit need be disregarded.

Still another object of the present invention is to provide a method forpreparing substrates for an information recording medium having flat andsmooth surfaces, which are optically isotropic without warping, withgood mold releasability and improved durability of the mold for casting.

Further, it is also an object of the present invention to provide a moldfor molding of the substrates for an information recording medium, whichis capable of preparing substrates for information recording mediumwhich are optically isotropic without warping and have uneven preformatsformed on the surface and also have durability.

In accordance with an aspect of the present invention, there is provideda method for preparing a substrate for an information recording mediumwhich comprises injecting a liquid resin into a mold for cast molding ofa substrate for an information recording medium having a plurality ofunits of mold for cast molding an uneven preformat pattern on thesurface arranged therein and solidifying the resin.

In accordance with another aspect of the present invention, there isprovided a mold for molding a substrate for an information recordingmedium which comprises a plurality of units of mold for cast moldinghaving an uneven preformat pattern on the surface fixed with a fixingmember.

Thus, according to the mold for molding a substrate for an informationrecording medium and the method for preparing a substrate for aninformation recording medium of the present invention, the patterns areformed on the respective units, and the units are independent of eachother, whereby a mold formed of a plurality of units can be prepared atlow cost. Also, even when defects may be formed on one pattern, only thedefected unit needs to be replaced and therefore the production cost ofthe information recording medium can be remarkably reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 4, and FIGS. 10A and 10B are schematic cross-sectional viewsshowing the embodiments of the molds for molding a substrate forinformation recording medium according to the present invention.

FIGS. 5A-5F, 6A-6E, 7A-7F, 8A-8F, 9A-9E, and 11A-11E are schematiccross-sectional views showing the embodiments of the methods forpreparing substrates for information recording medium according to thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In the following, the present invention is to be described in detail byuse of the drawings.

The present invention is a method for preparing a substate forinformation recording medium according to the cast molding method byusing, for example, a mold for casting formed of a plural number ofunits, having a cross-sectional shape opposite to the uneven shapes suchas grooves for tracking and pits for information of an optical recordingmedium. The mold for casting is formed of a plural number of units ofthe present invention an has a structure in which a plural number ofunits 1 having one or a plurality of uneven preformat patterns arearranged and fixed with a fixing member 11A as shown in FIG. 1, and itis also desirable that each unit 1 may be freely detachable andexchangeable. As the fixing method to be employed here, there is themethod in which the units are fixed by screwing through a bonding member11a as shown in FIG. 1, or the method in which a fixing member 11c isarranged around the units to fix them as shown in FIG. 3. However, it isdesirable in these methods that there should be a void, or space, ofgenerally 10 mm or less, preferably in the range of 2 to 5 mm, betweenthe units, for thermal expansion by the reaction heat, etc. duringworking of the resin for casting, precision of registration and furtheras the cutting portion of the molded product. When the resin for castingis penetrated into the void portions between the units to be solidifiedtherein, a substrate having projections is prepared, but absence of suchprojection is preferable for continuous production of the substrate foran information recording medium, and further preferable with respect tomold releasability of the mass of the cured substrates for aninformation recording medium from the mold for molding.

Accordingly, when the void portions between the units are embedded witha fixing member 11a as shown in FIG. 1, it is preferable that the resinfor casting should be sealed from leaking through the fixing member, oralternatively through the sealing material 2a when a member for backingis used as the fixing member as shown in FIG. 4. The sealing material 2a(including the fixing member which acts as the sealing member) should bepreferably one which is not corroded by the resin for casting, andfurther has a thermal expansion coefficient approximate to the materialof the unit or can absorb the thermal expansion coefficient of the unit.

As such materials, there can be employed low melting glasses, lowmelting metals and resins, depending on the material of the units andthe material of the resin for casting.

As the low melting glass, there may be employed those having adifference in thermal expansion coefficient from the unit of 30×10⁻⁷mm/(mm° C.) or less, preferably 20×10⁻⁷ mm/(mm° C.) or less. Forexample, PbO-SiO₂ -ZnO system, PbO-Al₂ O₃ -SiO₂ -ZnO system, vanadiumphosphate system glasses may be employed.

As the low melting metal, metals having a melting point of 300° C. orlower may be employed, for example, eutectic solder, Pb, In, Sn andalloys thereof, but it is preferable to use an eutectic solder, In, etc.in view of releasability from the resin to be used for casting andmodulus of elasticity.

As the resin, either one of thermoplastic resin or thermosetting resincan be used, provided that it has solvent resistance not corroded by theresin for casting. For example, there can be used as the thermoplasticresin vinyl resin, styrene resin, acrylic resin, polycarbonate resin,acetate resin, polyester resin, imide resin, fluorine type resin,olefinic resin, and as the thermosetting resin, phenol resin, melamineresin, epoxy resin, urea resin, polyester resin, etc.

Further, among these, resins having a Young's modulus of 2 to 300kg/cm², particularly 2 to 80 kg/cm², may be preferably employed. Thatis, by making the Young's modulus 2 kg/cm² or higher, no deformationwill occur even under a minute pressure applied during injection of theliquid resin for casting, while various stresses applied during moldingcan be absorbed by making the Young's modulus 300 kg/cm² or less.

Further, in view of mold releasability from the resin for cast molding,mold releasability can be improved by use of a sealing material having acontact angle, as measured with water, of 100° or higher, and as suchresins, silicone resins or fluorine type resins, may preferablyemployed. In case of a material other than such resins the moldreleasability can be improved by applying the mold release treatment tothe members.

As the method for applying the mold release treatment to the resin, itcan be practiced by the method of coating or vapor depositing a moldrelease agent thereon.

As the mold release agent, in the case of coating, for example, fluorinetype resins, olefinic resin, silicone resins, etc. may be employed.Also, a plasma polymerized film of the monomers for these resins may beappropriately employed. It is also possible to use an adhesive as theresin, for the sealing material, such as acrylic adhesives, urethanetype, polysulfide type, butyl type, styrene-butadiene rubber type,polyvinyl chloride type, chloroprene rubber type, chlorosulfonatedpolyethylene type, and ethylene-propylene rubber type adhesives, etc.Mixtures of these may be also available.

Of these adhesives, as the adhesive particularly excellent in heatresistance and solvent resistance, epoxyacrylate type adhesives oradhesives containing epoxyacrylate may be particularly preferred.

Whereas, among the above listed members, low melting glass, low meltingmetal and adhesives can also function as both the sealing material andthe fixing member. For example, a mold for cast molding of the presentinvention can be obtained without use of another fixing member such asthe member for backing as shown in FIG. 2.

When the mold for cast molding formed of a plural number of units of thepresent invention is prepared by bonding after correction of therelative positions of the respective units, the mass of the substratesfor information recording medium obtained with this mold can be appliedwith, for example, the printing steps of a recording layer withoutcutting the mass into individual substrates for an information recordingmedium, whereby productivity can be further improved. As the method forpreparing such a mold, for example, the units can be adhered by use ofthe member for backing 5c as shown in FIG. 4 as the fixing member 11cand a UV-ray curable type adhesive as the adhesive 3. More specifically,when an adhesive of, for example, the thermosetting type is used as theadhesive to be used for this fixing, there ensues the problem ofmisregister by the stress due to shrinkage of the cured resin.Accordingly, as the characteristic of such adhesive, it is required tofix quickly without misregister after registration. As a kind of suchadhesive, UV-ray curable type adhesives can be used. When the UV-raycurable type adhesive is in an uncured state, a plural number of unitsfor molding (hereinafter written as unit) having unevenness such asgrooves for tracking, pits for information on the surface, are arrangedin the member for backing with registration by correcting the positionsbetween said units before curing of the above UV-ray curable typeadhesive to fix the arrangement. Subsequently, by filling the gapsbetween the units with a sealing material, a more preferable mold forcast molding according to the present invention can be obtained.

As another method, registration between the respective units is effectedby use of an implement etc., the gaps between the units are filled andfixed with a low melting glass, low melting metal or adhesive, followedby removal of the implement, to give the product as such or afteradhesion of a member for backing.

Further, when the fixing member or the sealing material for sealing thevoids between the units is made, the portion protruding from thesurfaces of the respective units as shown in FIGS. 10A and 10B in thepresent invention, the portions corresponding to the above fixedportions of the mass of the substrates for information recording mediumprepared become concave portions, and by forming a thickness not thickerthan the substrate, flash generated between the respective units in thesubstrate formed of a plural number of units can be prevented, wherebyinconveniences due to the flash in the preparation steps for a recordingmedium such as the step of forming a recording layer can be avoided.Also, since the concave portion of the substrate formed by the protrudedportion of the mold for cast molding can be utilized for convenientlymarking in the respective steps for preparation of recording medium,productivity in the preparation steps for a recording medium can beimproved.

In the present invention, the material for the unit is not particularlylimited, but conventional materials may be employed, including, forexample, glass plates, ceramics, metals, etc., and the substrate portionand the pattern portion of the unit may be either the same or differentmaterial.

Whereas, in a unit having a metal film subjected to patterning formed ona glass plate, the metal film is liable to be peeled off if thetemperature during sealing or fixing of the gaps between the units istoo high. For this reason, it is desirable that the bonding temperaturein bonding the units with a low melting glass is 500° C. or lower. Whensuch units are sealed or fixed with a low melting metal, in order toimprove adhesion between the glass plate of the unit and the low meltingmetal, it is preferable to attach a metal film by sputtering, vapordeposition, etc. on the bonding surface of the unit and the low meltingmetal, namely the side surface of the unit, or the side surface and theback surface of the unit. For such metal film, chromium, titanium, etc.may be employed.

On the other hand, when a fixing member not functioning as the sealingmaterial, for example, a member for backing is employed, its material isnot particularly limited, but a broad scope of materials can beemployed, preferably the same material as the unit or the materialhaving a thermal expansion coefficient approximate to the unit such asthe low melting metal or the low melting glass as described above. Forexample, a glass plate, ceramics or metal, etc. with good thicknessprecision and flatness can be used.

The number of uneven preformat patterns formed on these units may bedetermined depending on the yield, cost, etc. of the substrate for aninformation recording medium prepared by forming grooves for tracking,pits for information, etc. For example, the mold for casting in the caseof preparing a substrate for an optical card is capable of patterning ofthe two planes by means of a 6-inch laser exposure machine, andtherefore the two planes may be used as one unit and said unit can bebonded in plural number, whereby a mold for casting with a number ofunits multiplied by 2 can be prepared.

Also, in the present invention, the number of units to be fixed may beany of 2 or more. For example, 9 or 12 units can be fixed, or a greaternumber of units can be fixed.

By use of the mold for casting prepared as described above, a liquidtransparent resin can be injected into the mold for casting in aconventional casting method to be solidified, followed by demolding, togive a substrate for an information recording medium.

The liquid resin to be injected into the mold for casing in the presentinvention may be a transparent uncured thermosetting resin, aphotocurable resin or unpolymerized thermoplastic resin. For example,the thermosetting resin may include phenol resin, epoxy resin, polyesterresin, etc., while the thermoplastic resin may include vinyl resin,styrene resin, acrylic resin, polycarbonate resin, acetate resin,polyester resin, etc.

As described above, by the mold for molding the substrate for aninformation recording medium and the method for an preparing thesubstrate for information recording medium according to the presentinvention, the units having uneven patterns on the surface correspondingto the uneven preformat pattern on the substrate for an informationrecording medium are mutually bonded to each other to give a mold forcasting. The substrates for an information recording medium inproportion to the number of units bonded by a one pass molding processcan be prepared, and also the units will receive no damage by mechanicalshock received during molding working owing to bonding mutually betweenthe units. Further, since the member for bonding the units to each otherhas excellent releasability relative to the resin to be cast molded,demolding after cast molding can be done with ease. Thus, the presentinvention can provide a mold for molding and a method for preparationthereof, which can prepare substrates for an information recordingmedium having a flat and smooth surface, which is optically isotropicwithout warping, and with improved durability of the mold for casting.

EXAMPLE 1

A mold for molding according to the present invention is to be describedby referring to FIG. 1.

1 is a unit with a size of 12.5 cm×12.5 cm comprising a nickel platehaving a groove for tracking and pits for information formed by lasercut on the surface. With this as one unit, a plural number of units wereprepared. Next, these units 1 were bonded with a bonding member 11a. Thebonding member 11A is made of aluminum die cast and fixed with a bolt.Also, this fixing member is a member subjected sufficiently to sealingso that no liquid resin during casting will be leaked out, and each unitis exchangeable by removing the bolt.

By use of the mold for cast molding obtained as described above, a resinwith the following composition was injected and polymerization wascarried out at 130° C. for 6 hours to prepare a mass of the substratesfor information recording medium.

    ______________________________________                                        [Formulated composition]                                                      ______________________________________                                        Methyl methacrylate 70    parts by weight                                     tert-Butyl methacrylate                                                                           25    parts by weight                                     Polyethylene glycol 5     parts by weight                                     dimethacrylate (MW 620)                                                       ______________________________________                                    

When the mass of the substrates for information recording medium was cutand its birefringence was examined, phase contrast within a cardsubstrate of 54 mm in length, 86 mm in width and 0.4 mm in thickness wasfound to be 0.1 to 3 nm, with no warping of the substrate beingobserved.

EXAMPLE 2

The preparation process for the mold for molding according to thepresent invention is to be described consecutively by referring to FIG.5.

First, 1 is a unit with a size of 12.5 cm×12.5 cm comprising a nickelplate having a groove for tracking with a width of 3 μm and a pitch of12 μm and an uneven preformat pattern which will become the pit forinformation formed on the surface, and with this as one unit, a pluralnumber of units are prepared.

Next, the above units were bonded to each other by use of a polyurethanetype adhesive as the fixing member 11b.

Further, for achieving a positional precision of each unit 1 and arigidness of the mold, the member for backing 4 may be adhered on theback surface of each unit 1 through the same adhesive 3 as the adhesive2.

Next, the mold obtained as described above and another glass plate 5subjected on the surface to optical polishing are arranged as opposed toeach other, and a spacer 6 is provided therearound to assemble a cell.

Into said cell is injected as the liquid resin 7 an uncured epoxy resinhaving the following formulated composition, followed by curing at 100°C. for 10 hours.

    ______________________________________                                        [Formulated composition]                                                      ______________________________________                                        Bisphenol A type epoxy resin                                                                      100    parts by weight                                    Methylhexahydrophthalic                                                                           88     parts by weight                                    anhydride                                                                     2-Ethyl-4-methylimidazole                                                                         0.5    part by weight                                     2,6-Di-tert-butyl-p-cresol                                                                        1.0    part by weight                                     ______________________________________                                    

Next, after demolded from the mold as shown in FIG. 11D, the substrateformed of a plural number of unit surfaces was cut into predeterminedsizes to obtain a substrate 9 for information recording medium (see FIG.11C).

When the birefringence of the substrate for information recording mediumobtained was examined, the phase contrast within a card substrate of 54mm in length, 86 mm in width and 0.4 mm in thickness was found to be 0.1to 5 nm, with no warping of the substrate being observed.

EXAMPLE 3

FIG. 3 is a sectional view showing the structure of the mold for castmolding to be used in Example 3 of the present invention.

1 is a unit prepared according to the same method as prepared inExamples 1, 2, and 11c shows a frame as the fixing member. Also, forthis member, either a metal or a heat-resistant resin can be used.Further, by providing a thickness as the spacer at the outercircumference of the frame, the bonding member and the spacer can beintegrated. By use of the mold for cast molding obtained as describedabove, a substrate was prepared according to the same method as inExample 1.

In the case of this Example 3, bonding of the respective units and thespacer can be integrated. When the birefringence of the substrate forinformation recording medium was examined, the phase contrast within acard substrate of 54 mm in length, 86 mm in width and 0.4 mm inthickness was found to be 0.1 to 5 nm, with no warping of the substratebeing observed.

EXAMPLE 4

Example 4 is described by referring to FIG. 5. 1 is a unit comprising aglass plate prepared similarly as in Example 2, and a plural number ofthe units were prepared.

Next, said units were adhered to each other by use of an acrylic rubbertype adhesive controlled to a Young's modulus of 35 kg/cm² during curingof the resin for cast molding at the fixing member 11 to be bonded.

Also, in order to obtain a positional precision of each unit and arigidness as the mold, it is desirable to adhere the member for backing4 through the same adhesive 3 as the adhesive 2 on the back of eachunit 1. As the member for backing 4, a glass plate having a sufficientthickness precision and flatness was used.

Next, with the mold obtained and another glass plate 5 subjected on thesurface to optical polishing arranged as opposed to each other through aspacer, a cell is assembled.

Into said cell is injected a liquid epoxy resin having the followingformulated composition as the liquid resin, followed by curing at 100°C. for 10 hours.

    ______________________________________                                        [Formulated composition]                                                      ______________________________________                                        Bisphenol A type epoxy resin                                                                      100    parts by weight                                    Methylhexahydrophthalic                                                                           88     parts by weight                                    anhydride                                                                     2-Ethyl-4-methylimidazole                                                                         0.5    part by weight                                     2,6-Di-tertiary-butyl-p-cresol                                                                    1.0    part by weight                                     ______________________________________                                    

Next, after demolded from the mold, the substrate formed of a pluralnumber of unit surfaces was cut into predetermined sizes to obtain asubstrate for information recording medium.

When the birefringence of the substrate for information recording mediumobtained was examined, the phase contrast within a card substrate of 54mm in length, 86 mm in width and 0.4 mm in thickness was found to be 0.1to 5 nm, with no warping of the substrate being observed.

EXAMPLE 5

Into the cell assembled similarly as in Example 4, a resin having thefollowing composition is injected and polymerization is carried out at130° C. for an 6 hours, and following otherwise the same procedure as inExample 4, a substrate for information recording medium was obtained.

When the birefringence of the substrate for information recording mediumobtained was examined, the phase contrast within a card substrate of 54mm in length, 86 mm in width and 0.4 mm in thickness was found to be 0.1to 3 nm, with no warping of the substrate being observed.

    ______________________________________                                        [Formulated composition]                                                      ______________________________________                                        Methyl methacrylate 70    parts by weight                                     Tertiary-butyl methacrylate                                                                       25    parts by weight                                     Polyethylene glycol 5     parts by weight                                     dimethacrylate (MW 620)                                                       ______________________________________                                    

COMPARATIVE EXAMPLE 1

As Comparative example 1, a substrate for cast molding was prepared byuse of an epoxy type resin of the bisphenol A type in general as theadhesive, and a substrate was prepared according to the same steps as inExample 4.

When durability of the mold for casting of Example 4 and Comparativeexample 1 was evaluated, no particular inconvenience occurred even whencast molding was repeated for 100 times, but a part of the units withinthe mold was peeled off after about 50-th molding, whereby there ensueda problem in thickness precision of the substrate.

EXAMPLE 6

FIGS. 6A to 6E illustrate the process showing an example of the methodfor preparation of the information recording medium of the presentinvention. All of the Figures show the cross-sections of the substrate.

The preparation process is now described consecutively by referring tothe drawings.

First, in FIG. 6A, in a groove of high precision, a plural number ofunits 1 having chromium film formed on a glass plate according to thephotolithographic steps were prepared to provide each single unit.

Next, after correction of the position of the unit, the position of theunit is quickly fixed by use of an implement, and a low melting glass ofthe PbO-SiO₂ -ZnO system is filled as the bonding member in the gaps ofabout 3 mm in width between the units and heated to 400° C. to melt thelow melting glass, thereby effecting fixing and sealing between theunits (FIG. 6B).

In this case, when a blue glass plate is used for the unit, since it hasa thermal expansion ratio of about 90 to 100×10⁻⁷ mm/(mm° C.), thethermal expansion ratio of the low melting glass is made 100 to 110×10⁻⁷mm/(mm° C.). The low melting glass has a Tg of 320° C. and the bondingtemperature is sufficiently 400° C.

Next, the unit is removed from the implement and a member for backing isadhered by use of Cemedine 1565 (produced by Cemedine K.K.) as theadhesive (FIG. 6C).

Next, as shown in FIG. 6D, the mold obtained as described above anotherglass plate 5 subjected on the surface to optical polishing is arrangedso as to be opposite to each other and a spacer 6 is providedtherearound to assemble a cell. Into said cell was injected a resinhaving the following formulated composition as the liquid resin 7, andpolymerization is carried out at 120° C. for 10 hours.

    ______________________________________                                        [Formulated composition]                                                      ______________________________________                                        Methyl methacrylate 70    parts by weight                                     Tertiary-butyl methacrylate                                                                       25    parts by weight                                     Polyethylene glycol 5     parts by weight                                     dimethacrylate (MW 620)                                                       ______________________________________                                    

Next, as shown in FIG. 6E, an information substrate 8 for informationrecording medium formed of a plural number of units is obtained bydemolding from the mold.

When the birefringence of the substrate obtained was examined, the phasecontrast was found to be sufficiently small as 0.1 to 0.5 nm within acard substrate of 54 mm in length, 86 mm in width and 0.4 mm inthickness, and there was no warping of the substrate observed.

EXAMPLE 7

FIGS. 7A to 7F illustrate the process showing an example of the methodfor preparation of the information recording medium of the presentinvention. All of the Figures show the cross-sections of the substrate.

The preparation process is now described consecutively by referring tothe drawings.

First, in FIG. 7A, in a groove of high precision, a plural number ofunits 1 having chromium film formed on a glass plate according to thephotolithographic steps is prepared to provide each one unit.

As shown in FIG. 7B, the above unit 1 is set in a vacuum chamber andmetal film 21 is adhered by spattering on the surface which a Chromiumfilm is not formed. The spattering was conducted by introducing Ar gasof 20 m Torr and at a power of 1 kW with a R.F magnetron. Since Chromiumis spattered evenly around the unit by spattering, a Chromium film isadhered simultaneously on the side and back surface.

Next, after correction of the position of the unit, the position of theunit is quickly fixed by use of an implement, and the gaps between theunits with a width of about 3 mm are bonded with a low melting metal 5.For the low melting metal, an eutectic solder is used, and the eutecticsolder is heated to 200° C. to be melted without void into the gapsbetween the units, thereby effecting fixing and sealing between theunits (FIG. 7C).

Next, the unit was removed from the implement and a member for backingis adhered by use of Cemedine 1565 (produced by Cemedine K.K.) as theadhesive (FIG. 7D).

Next, as shown in FIG. 7E, the mold obtained as described above hasanother glass plate 5 subjected on the surface for optical polishing andarranged so as to be opposite to each other and a spacer 6 is providedtherearound to assemble a cell. Into said cell is injected a resinhaving the following formulated composition as the liquid resin 7, andpolymerization is carried out at 120° C. for 10 hours.

    ______________________________________                                        [Formulated composition]                                                      ______________________________________                                        Methyl methacrylate 70    parts by weight                                     Tertiary-butyl methacrylate                                                                       25    parts by weight                                     Polyethylene glycol 5     parts by weight                                     dimethacrylate (MW 620)                                                       ______________________________________                                    

Next, as shown in FIG. 7F, a substrate 9 for an information recordingmedium formed of a plural number of units is obtained by demolding fromthe mold.

When the birefringence of the substrate obtained was examined, the phasecontrast within a card substrate of 54 mm in length, 86 mm in width and0.4 mm in thickness was sufficiently small as 0.1 to 0.5 nm, and also nowarping of the substrate was observed.

EXAMPLE 8

By use of FIGS. 5A to 5F, an example of the method for preparation ofthe substrate for an information recording medium is shown. All of theFigures show the cross-sections of the substrate.

The preparation process is now described consecutively by referring tothe drawings.

First, in FIG. 5A, a plural number of units 1 comprising a glass platehaving a groove of high precision formed thereon are prepared to providethem respectively as one unit.

Next, in FIG. 5B, the above units 1 are bonded together with a fixingmember 11b. In this Example, a silicone adhesive is used for the fixingmember, but fluorine resin type adhesives are also available as otherExamples. Also, for obtaining the positional precision as each unit 1and the rigidity of the mold, it is desirable to adhere a member forbacking through an adhesive 3 such as epoxy type, silicone type,polyester type and acrylic type on the back of each unit 1. As themember for backing 4, a glass plate or metal with good thicknessprecision and flatness is used.

Next, as shown in FIG. 5C, the mold obtained as described above andanother glass plate 5 subjected on the surface to optical polishing arearranged opposite to each other, and a spacer 6 is provided therearoundto assemble a cell.

Into the cell is injected a liquid epoxy resin having the followingformulated composition as the liquid resin 7, followed by curing at 100°C. for 10 hours.

    ______________________________________                                        [Formulated composition]                                                      ______________________________________                                        Bisphenol A type epoxy resin                                                                      100    parts by weight                                    Methylhexahydrophthalic                                                                           88     parts by weight                                    anhydride                                                                     2-Ethyl-4-methylimidazole                                                                         0.5    part by weight                                     2,6-Di-tertiary-butyl-p-cresol                                                                    1.0    part by weight                                     ______________________________________                                    

Next, after being demolded from the mold as shown in FIG. 5E, thesubstrate formed of a plural number of unit surfaces is cut intopredetermined sizes to obtain a substrate 9 for an information recordingmedium (see FIG. 5F).

When the birefringence of the substrate obtained was examined, the phasecontrast within a card substrate of 54 mm in length, 86 mm in width and0.4 mm in thickness was 0.1 to 5 nm, without striae, etc. due to poormold releasability of the substrate, and no wrap was also observed.

EXAMPLE 9

A plural number of units comprising a nickel plate having a groove fortracking and pits for information formed by laser cut on the surface areprepared, and these units were bonded with a fixing member. The fixingmember is made of, for example, a silicone resin, Teflon resin, etc.,each of which has a contact angle of 100° or lower, and which is amember enabling sufficient sealing so that no liquid resin will beleaked out during cast molding, and also has a detachable structure.

By use of the mold for molding obtained as described above, a cell isassembled similarly as described in Example 1, and an acrylic resinhaving the following formulated composition is injected thereinto as theliquid resin, followed by polymerization at 130° C. for 6 hours.

    ______________________________________                                        [Formulated composition]                                                      ______________________________________                                        Methyl methacrylate 70    parts by weight                                     Tertiary-butyl methacrylate                                                                       25    parts by weight                                     Polyethylene glycol 5     parts by weight                                     dimethacrylate (MW 620)                                                       ______________________________________                                    

Next, after demolding from the mold, the substrate formed of a pluralnumber of units is cut into predetermined sizes to obtain a substratefor an information recording medium.

When the birefringence of the information recording medium was examinedsimilarly as in Example 1, the phase contrast within a card substratewas found to be 0.1 to 3 nm, without striae, etc. due to poor moldreleasability of the substrate, and no warp was observed.

The following Table 1 shows evaluation when various members for bondingthe units are employed.

From the Table, it can be seen that the evaluation is 90 for adhesivesof the fluorine type and the silicone type with a contact angle withwater of 100° or more, but the evaluation for the adhesives with thecontact angle of less than 100° of the ethylene type et seq is 65 orless to give poor yield.

                  TABLE 1                                                         ______________________________________                                        Bonding member                                                                              Contact angle (water)                                                                        Evaluation                                       ______________________________________                                        Fluorine type 120°    90                                               Silicone type 110°    90                                               Ethylene type 98°     65                                               Epoxy type    89°     50                                               Acryl type    83°     45                                               Nylon type    76°     35                                               ______________________________________                                    

The contact angle in the present invention is a value measured in a roommaintained at 20°±2° C. by use of a Contact-Angle Meter CA-D (producedby Kyowa Kaimen Kagaku).

EXAMPLE 10

FIGS. 8A to 8F illustrate the process showing an example of the methodfor preparation of the information recording medium of the presentinvention. All of the Figures show the cross-sections of the substrate.

The preparation process is now described consecutively by referring tothe drawings.

First, in FIG. 8A, a plural number of units 1 comprising a glass platehaving a groove of high precision formed according to thephotolithographic steps are prepared to provide them respectively as oneunit.

Next, in FIG. 8B, by use of the adhesive 3, the above units 1 arearranged on a member for backing as the fixing member. As the UV-raycurable type adhesive, Locktite UV-ray curable type adhesive LI-298-661(produced by Nippon Locktite K.K.), a photocurable type adhesive DiabondDA855G, UV130 (produced by Nogawa Chemical K.K.), etc. can be used.

Also, as the fixing member 11e, a glass substrate with good thicknessprecision and flatness can be used.

Next, as shown in FIG. 8C, after effecting registration by correctingthe positions of the units, as shown in FIG. 8D, UV-ray is irradiatedquiclkly to fix the positions of the units. At this time, UV-ray may beirradiated in either direction from the unit side or from the memberside for backing, but it is required that the side to be irradiatedshould be made transmissive of UV-ray.

Next, as shown in FIG. 8E, the mold obtained as described above andanother glass plate 5 subjected on the surface to optical polishing arearranged opposite to each other and a spacer 6 is provided therearoundto assemble a cell. Into said cell is injected a liquid acryl resinhaving the following formulated composition as the liquid resin 7,followed by curing at 120° C. for 10 hours.

    ______________________________________                                        [Formulated composition]                                                      ______________________________________                                        Methyl methacrylate 70    parts by weight                                     Tertiary-butyl methacrylate                                                                       25    parts by weight                                     Polyethylene glycol 5     parts by weight                                     dimethacrylate (MW 620)                                                       ______________________________________                                    

Next, as shown in FIG. 8F, a substrate for information recording medium7 is obtained by demolding from the mold.

When birefringence of the substrate for information recording mediumobtained was examined, the phase contrast within a card of 54 mm inlength, 86 mm in width and 0.4 mm in thickness was found to be 0.1 to 5nm, without warping of the substrate being observed.

Also, since the uneven preformats formed on the mass 7 of the substratesfor an information recording medium are each subjected to registration,recording layers could be formed before cutting into individualsubstrates for information recording medium, whereby productivity couldbe further improved.

EXAMPLE 11

FIGS. 9A to 9E illustrate the process showing an example of the methodfor preparation of the information recording medium of the presentinvention. All of the Figures show the cross-sections of the substrate.

The preparation process is now described consecutively by referring tothe drawings.

First in FIG. 9A, a plural number of units 1 comprising a glass platehaving a groove of high precision formed according to thephotolithographic steps are prepared to provide them respectively as oneunit.

Next, in FIG. 9B, by use of the adhesive 3, the above units 1 arearranged on a member for backing as the fixing member 11e.

As the adhesive, UV-1000 which is an epoxy acrylate type adhesiveproduced by Sony Chemical K.K. is employed.

As the member for backing 3, a glass plate with good thickness precisionand flatness is employed.

Next, after the position of the unit is corrected, UV-ray is quicklyirradiated to fix the position of the unit. At this time, UV-ray may beirradiated in either direction from the unit side or from the memberside for backing, but it is required that the side to be irradiatedshould be made transmissive of UV-ray.

Next, as shown in FIG. 9C, a sealing material 2a is filled in the gapsof about 3 mm in width between the units. As the sealing material, anepoxy acrylate type UV-1000 was used. After filling, the sealingmaterial is cured by irradiation of UV-ray.

Next, as shown in FIG. 9D, the mold obtained as described above andanother glass plate 5 subjected on the surface to optical polishing arearranged opposite to each other, and a spacer 6 is provided therearoundto assemble a cell.

Into said cell is injected a liquid acrylic resin having the followingformulated composition as the liquid resin 7, followed by curing at 120°C. for 10 hours.

    ______________________________________                                        [Formulated composition]                                                      ______________________________________                                        Methyl methacrylate 70    parts by weight                                     Tertiary-butyl methacrylate                                                                       25    parts by weight                                     Polyethylene glycol 5     parts by weight                                     dimethacrylate (MW 620)                                                       ______________________________________                                    

Next, as shown in FIG. 9E, a substrate for information recording medium8 is obtained by demolding from the mold.

When birefringence of the substrate for information recording mediumobtained was examined, the phase contrast within a card of 54 mm inlength, 86 mm in width and 0.4 mm in thickness was found to be 0.1 to 5nm, with no warping of the substrate being observed.

EXAMPLE 12

FIGS. 9A to 9E illustrate the process showing an example of the methodfor preparation of the substrate for information recording medium of thepresent invention. All of the Figures show the cross-sections of thesubstrate.

The preparation process is now described consecutively by referring tothe drawings.

First in FIG. 9A, a plural number of units 1 comprising a glass platehaving a groove of high precision formed according to thephotolithographic steps are prepared to provide them respectively as oneunit.

Next, in FIG. 9B, by use of the adhesive 3, the above units are arrangedon a fixing member 11e. At this time, as the adhesive, Locktite UV-raycurable type adhesive LI-298, 661, etc. are employed.

As the fixing member 11e, a glass plate with good thickness precisionand flatness is employed.

Next, after the position of the unit is corrected, UV-ray is quicklyirradiated to fix the position of the unit. At this time, UV-ray may beirradiated in either direction from the unit side or from the memberside for backing, but it is required that the side to be irradiatedshould be made transmissive of UV-ray.

Next, as shown in FIG. 9C, a sealing material 2a is filled in the gapsof about 2.5 mm in width between the units. As the thermosetting resin,a bismaleimide-triazine resin (produced by Mitsubishi Gas Kagaku K. K.)was employed. After defoaming, filling and further defoaming, heating iseffected at 80° C. for 6 hours, then the temperature is elevated from80° C. to 175° C. in 2 hours, followed by heating at 175° C. for 8 hoursto cure the resin.

Next, as shown in FIG. 9D, the mold obtained as described above andanother glass plate 5 subjected on the surface to optical polishing arearranged so as to be opposite to each other, and a spacer 6 is providedtherearound to assemble a cell.

Into said cell is injected a liquid acrylic resin having the followingcomposition as the liquid resin 7, followed by curing at 120° C. for 10hours.

    ______________________________________                                        [Formulated composition]                                                      ______________________________________                                        Methyl methacrylate 70    parts by weight                                     Tertiary-butyl methacrylate                                                                       25    parts by weight                                     Polyethylene glycol 5     parts by weight                                     dimethacrylate (MW 620)                                                       ______________________________________                                    

Next, as shown in FIG. 9E, the product is demolded from the mold to givea substrate for information recording medium 8.

When birefringence of the substrate for information recording mediumobtained was examined, the phase contrast within a card of 54 mm inlength, 86 mm in width and 0.4 mm in thickness was found to be 0.1 to 5nm, with no warping of the substrate being observed.

EXAMPLE 13

FIGS. 9A to 9E illustrate the process showing an example of the methodfor preparation of the substrate for information recording medium of thepresent invention. All of the Figures show the cross-sections of thesubstrate.

The preparation process is now described consecutively by referring tothe drawings.

First, in FIG. 9A, a plural number of units 1 comprising a glass platehaving a groove of high precision formed according to thephotolithographic steps are prepared to provide them respectively as oneunit.

Next, in FIG. 9B, by use of the adhesive 3, the above units are arrangedon a fixing member 11e. At this time, as the adhesive, Diabond BA855G,UV 130 of the UV-ray curable type adhesive (produced by Nogawa ChemicalK.K.), etc. is employed.

As the fixing member 11, a glass plate with good thickness precision andflatness is employed.

Next, after the position of the unit is corrected, UV-ray is quicklyirradiated to fix the position of the unit. At this time, UV-ray may beirradiated in either direction from the unit side or from the memberside for backing, but it is required that the side to be irradiatedshould be made transmissive of UV-ray.

Next, as shown in FIG. 9C, a sealing material 2a is filled in the gapsof about 3.5 mm between the units. As the thermoplastic resin, Sony BondSC608 (produced by Sony Chemical K.K.) was employed. After filling, theresin is solidified by heating at 100° C. for 180 minutes.

Next, as shown in FIG. 9D, the mold obtained as described above andanother glass plate 5 subjected on the surface to optical polishing arearranged so as to be opposite to each other, and a spacer 6 is providedtherearound to assemble a cell.

Into said cell is injected a liquid epoxy resin having the followingformulated composition as the liquid resin 7, followed by curing at 100°C. for 10 hours.

    ______________________________________                                        [Formulated composition]                                                      ______________________________________                                        Bisphenol A type epoxy resin                                                                      100    parts by weight                                    Methylhexahydrophthalic                                                                           88     parts by weight                                    anhydride                                                                     2-Ethyl-4-methylimidazole                                                                         0.5    part by weight                                     2,6-Di-tert-butyl-p-cresol                                                                        1.0    part by weight                                     ______________________________________                                    

Next, as shown in FIG. 1E, the product is demolded from the mold to givea substrate for information recording medium 8.

When the birefringence of the substrate for information recording mediumobtained is examined, the phase contrast within a card substrate of 54mm in length, 86 mm in width and 0.4 mm in thickness is found to be 0.1to 5 nm, with no warping of the substrate being observed.

EXAMPLE 14

FIGS. 9A to 9F illustrate the process showing an example of the methodfor preparation of the substrate for information recording medium of thepresent invention. All of the Figures show the cross-sections of thesubstrate.

The preparation process is now described consecutively by referring tothe drawings.

First, in FIG. 9A, a plural number of units 1 comprising a glass platehaving a groove of high precision formed according to thephotolithographic steps is prepared to provide them respectively as oneunit.

Next, in FIG. 9B, by use of the adhesive 3, the above units are arrangedon a fixing member 11e. At this time, as the adhesive, Diabond DA855G ofthe UV-ray curable type adhesive (produced by Nogawa Chemical K.K.) wasemployed.

As the fixing member 11e, a glass plate with good thickness precisionand flatness is employed.

Next, after the position of the unit is corrected, UV-ray was quicklyirradiated to fix the position of the unit. At this time, UV-ray may beirradiated in either direction from the unit side or from the memberside, but it is required that the side to be irradiated should be madetransmissive of UV-ray.

Next, in FIG. 9C, the gaps of about 4 mm in width between the units weresealed with a sealing material 2. As the sealing material, Sony BondUV1000 (an acrylic resin, produced by Sony Chemical) is employed. Afterfilling, the resin is cured by irradiation of UV-ray.

On the sealing material, as shown in FIG. 9D, Frekote 44 produced byFricoat Co., U.S.A., is applied to a thickness of about 4 mm, followedby drying, thus applying mold release treatment, to form a mold releasedportion 5.

Next, as shown in FIG. 9E, the mold obtained as described above andanother glass plate 5 subjected on the surface to optical polishing arearranged so as to be opposite to each other, and a spacer 6 is providedtherearound to assemble a cell.

Into said cell is injected a liquid acrylic resin having the followingformulated composition, followed by curing at 120° C. for 10 hours.

    ______________________________________                                        [Formulated composition]                                                      ______________________________________                                        Methyl methacrylate 70    parts by weight                                     Tertiary-butyl methacrylate                                                                       25    parts by weight                                     Polyethylene glycol 5     parts by weight                                     dimethacrylate (MW 620)                                                       ______________________________________                                    

Next, as shown in FIG. 9F, the product is demolded from the mold to givea substrate for information recording medium 8. The mold releasabilitywas good, and the connecting portion of the substrate corresponding tothe portion between the units was found to be smooth without anyprojection.

When birefringence of the substrate for information recording mediumobtained was examined, the phase contrast within a card substrate of 54mm in length, 86 mm in width and 0.4 mm in thickness was found to be 0.1to 5 nm, with no warping of the substrate being observed. There was nostriae of the substrate due to poor releasability, neither.

EXAMPLE 15

FIGS. 11A to 11E illustrate the process showing an example of the methodfor preparation of the substrate for information recording medium of thepresent invention. All of the Figures show the cross-sections of thesubstrate.

The preparation process is now described consecutively by referring tothe drawings.

First, in FIG. 11A, a plural number of units 1 comprising a glass platehaving a groove of high precision formed according to thephotolithographic steps are prepared to provide them respectively as oneunit.

FIG. 2 shows a mold for casting having the above units 1 adhered to eachother with an adhesive 3a. As the kind of the adhesive, one havingadhesiveness to glass plate, and also having too firm adhesive force isnot suitable for making exchange of units easier. In this Example, anacrylic rubber type adhesive is used, but a urethane type adhesive, apolysulfide type adhesive may be also available. Also, for exhibitingpositional precision and rigidity as the mold of each unit 1, it isdesirable to adhere a member 4 for backing through the same adhesive 3bas the adhesive 3a on the back of each unit 1. And, prior to curing ofthe adhesive 3a, a sealing member 2a for protrusion is adhered thereonto form a protruded portion. As the material for the member forprotrusion 2a, a heat-resistant resin, glass or metal may be employed.This mold may be subjected to mold release treatment, if desired, toprovide a mold for casting.

Next, as shown in FIG. 11C, the mold obtained as described above andanother glass plate 5 subjected on the surface to optical polishing arearranged so as to be opposite to each other and a spacer 6 providedtherearound to assemble a cell.

Into said cell is injected a liquid epoxy resin having the followingformulated composition as the liquid resin 7, followed by curing at 100°C. for 10 hours.

    ______________________________________                                        [Formulated composition]                                                      ______________________________________                                        Bisphenol A type epoxy resin                                                                      100    parts by weight                                    Methylhexahydrophthalic                                                                           88     parts by weight                                    anhydride                                                                     2-Ethyl-4-methylimidazole                                                                         0.5    part by weight                                     2,6-Di-tert-butyl-p-cresol                                                                        1.0    part by weight                                     ______________________________________                                    

Next, after the product is demolded from the mold as shown in FIG. 11D,the substrate formed of a plural number of units is cut intopredetermined sizes to obtain a substrate for information recordingmedium 9. (see FIG. 11E).

When the birefringence of the substrate for information recording mediumobtained was examined, the phase contrast within a card substrate of 54mm in length, 86 mm in width and 0.4 mm in thickness was found to be 0.1to 5 nm, with no warping of the substrate being observed.

The substrate prepared as described above, on which marking is appliedwith the members for protrusion 2a can utilize them as the marks forregistration in the respective steps during preparation of the recordingmedium.

We claim:
 1. A mold for molding a plurality of substrates for aninformation recording medium, said mold comprising:a fixing member; aplurality of units fixed to said fixing member, each of the units has onits surface a preformat pattern with a surface corresponding to theinformation recording medium; and a molding cavity disposed opposite tosaid units so that said preformat patterns face said molding cavity. 2.A mold for molding substrates for an information recording mediumaccording to claim 1, wherein each of said units is detachable.
 3. Amold for molding substrates for an information recording mediumaccording to claim 1, further comprising a backing member to which saidunits are adhered.
 4. A mold for molding substrates for an informationrecording medium according to claim 1, wherein said fixing member is abacking member.
 5. A mold for molding substrates for an informationrecording medium according to claim 4, wherein said units are fixed ontosaid fixing member with a UV-ray curable type adhesive.
 6. A mold formolding substrates for an information recording medium according toclaim 5, wherein a plurality of said units are arranged on said fixingmember when said UV-ray curable type adhesive is in an uncured state andthen fixed by curing of the UV-ray curable type adhesive.
 7. A mold formolding substrates for an information recording medium according toclaim 1, having voids between said units.
 8. A mold for moldingsubstrates for an information recording medium according to claim 7,wherein said voids are 10 mm or less.
 9. A mold for molding of asubstrate for information recording medium according to claim 8, whereinsaid voids are 2 to 5 mm.
 10. A mold for molding substrates aninformation recording medium according to claim 7, further comprising asealing material sealing said voids between said units.
 11. A mold formolding substrates for an information recording medium according toclaim 10, wherein a mold release treatment is applied on said sealingmaterial.
 12. A mold for molding substrates for an information recordingmedium according to claim 10, wherein said sealing material is notcorroded by the resin for cast molding.
 13. A mold for moldingsubstrates for an information recording medium according to claim 12,wherein said sealing material is a low melting glass.
 14. A mold formolding substrates for an information recording medium according toclaim 13, wherein the difference between the thermal expansion ratio ofsaid low melting glass and the thermal expansion ratio of said units is30×10⁻⁷ /°C. or less
 15. A mold for molding substrates for aninformation recording medium according to claim 13, wherein thedifference between the thermal expansion ratio of said low melting glassand the thermal expansion ratio of said units is 20×10⁻⁷ /°C. or less.16. A mold for molding substrates for an information recording mediumaccording to claim 12, wherein said sealing material is a low meltingmetal.
 17. A mold for molding substrates for an information recordingmedium according to claim 16, wherein the melting point of said lowmelting metal is 300° C. or lower.
 18. A mold for molding substrates foran information recording medium according to claim 12, wherein saidsealing material is a resin.
 19. A mold for molding substrates for aninformation recording medium according to claim 18, wherein said resinis a thermosetting resin.
 20. A mold for molding substrates for aninformation recording medium according to claim 18, wherein said resinis an adhesive.
 21. A mold for molding substrates for an informationrecording medium according to claim 20, wherein said adhesive is anepoxy acrylate type adhesive.
 22. A mold for molding substrates for aninformation recording medium according to claim 18, wherein said resinhas a Young's modulus of 2 to 300 kg/cm².
 23. A mold for moldingsubstrates for an information recording medium according to claim 18,wherein said resin has a Young's modulus of 2 to 80 kg/cm².
 24. A moldfor molding substrates for an information recording medium according toclaim 10, wherein said sealing material is a material having a contactangle as measured with water of 100° or more.
 25. A mold for moldingsubstrates for an information recording medium according to claim 10,wherein said sealing material protrudes from a surface of said units.26. A mold for molding substrates for an information recording mediumaccording to claim 1, wherein each said unit has a plurality ofpreformat patterns on its surface.
 27. A mold for molding substrates foran information recording medium according to claim 1, wherein said moldis for cast molding.
 28. A mold for molding a substrate for aninformation recording medium, said mold comprising:a bonding member; aplurality of units bonded to said bonding member, each unit having onits surface a preformat pattern corresponding to the informationrecording medium and with a void formed between each unit, and a moldingcavity disposed opposite to said units so that said preformat patternsface said molding cavity, wherein said bonding member is a sealingmember for sealing the voids between said units.
 29. A mold according toclaim 28, further comprising a backing member to which said units areadhered.
 30. A mold according to claim 28, wherein the void is 10 mm orless.
 31. A mold according to claim 30, wherein the void is 2 to 5 mm.32. A mold according to claim 28, wherein a mold release treatment isapplied on said bonding member.
 33. A mold according to claim 28,wherein said bonding member is not corroded by the resin for castmolding.
 34. A mold according to claim 28, wherein said bonding memberis a low melting glass.
 35. A mold according to claim 34, wherein thedifference between the thermal expansion ratio of said low melting glassand the thermal expansion ratio of said units is 30×10⁻⁷ /°C. or less.36. A mold according to claim 34, wherein the difference between thethermal expansion ratio of said low melting glass and the thermalexpansion ratio of said units is 20×10⁻⁷ /°C. or less.
 37. A moldaccording to claim 28, wherein said bonding member is a low meltingmetal.
 38. A mold according to claim 37, wherein the melting point ofsaid low melting metal is 300° C. or lower.
 39. A mold according toclaim 28, wherein said bonding member is a resin adhesive.
 40. A moldaccording to claim 39, wherein said adhesive is an epoxy acrylate-typeadhesive.
 41. A mold according to claim 39, wherein said adhesive has aYoung's modulus of 2 to 300 kg/cm².
 42. A mold according to claim 41,wherein said adhesive has a Young's modulus of 2 to 80 kg/cm².
 43. Amold according to claim 28, wherein said bonding member has a surfaceproperty of a contact angle as measured with water of 100° or more. 44.A mold according to claim 28, wherein said bonding member protrudes froma surface of said units.
 45. A mold according to claim 28, wherein eachsaid unit has a plurality of preformat patterns on its surface.
 46. Amold according to claim 28, wherein said mold is for cast molding.
 47. Amold for cast molding a plurality of substrates for an informationrecording medium, said mold comprising:a fixing member; and a pluralityof units fixed to said fixing member and having a void between eachunit, with each of the units having on its surface a preformat patterncorresponding to the information recording medium; and a sealingmaterial for sealing the voids between said units.
 48. A mold accordingto claim 47, wherein each of said units is detachable.
 49. A moldaccording to claim 47, further comprising a backing member to which saidunits are adhered.
 50. A mold according to claim 47, wherein said fixingmember is a backing member.
 51. A mold according to claim 50, whereinsaid units are fixed onto said fixing member with a UV-ray curable-typeadhesive.
 52. A mold according to claim 51, wherein a plurality of saidunits are arranged on the fixing member when said UV-ray curable-typeadhesive is in an under uncured state and then fixed by curing of theUV-ray curable-type adhesive.
 53. A mold according to claim 47, whereinthe void is 10 mm or less.
 54. A mold according to claim 53, wherein thevoid is 2 to 5 mm.
 55. A mold according to claim 47, wherein a moldrelease treatment is applied on said sealing material.
 56. A moldaccording to claim 47, wherein said sealing material is not corroded bythe resin for cast molding.
 57. A mold according to claim 47, whereinsaid sealing material is a low melting glass.
 58. A mold according toclaim 57, wherein the difference between the thermal expansion ratio ofsaid low melting glass and the thermal expansion ratio of said units is30×10⁻⁷ /°C. or less.
 59. A mold according to claim 58, wherein thedifference between the thermal expansion ratio of said low melting glassand the thermal expansion ratio of said units is 20×10⁻⁷ /°C. or less.60. A mold according to claim 47, wherein said sealing material is a lowmelting metal.
 61. A mold according to claim 60, wherein the meltingpoint of said low melting metal is 300° C. or lower.
 62. A moldaccording to claim 47, wherein said sealing material is a resin.
 63. Amold according to claim 62, wherein said resin is a thermosetting resin.64. A mold according to claim 63, wherein said resin is an adhesive. 65.A mold according to claim 64, wherein said adhesive is an epoxyacrylate-type adhesive.
 66. A mold according to claim 62, wherein saidresin has a Young's modulus of 2 to 300 kg/cm².
 67. A mold according toclaim 66, wherein said resin has a Young's modulus of 2 to 80 kg/cm².68. A mold according to claim 47, wherein said sealing material has asurface property of a contact angle as measured with water of 100° C. ormore.
 69. A mold according to claim 47, wherein said sealing materialprotrudes from a surface of said units.
 70. A mold according to claim47, wherein each of said units has a plurality of the preformat patternson its surface.